1. Field of the Invention
This invention relates to a toner supplying device included in an image forming apparatus.
2. Discussion of the Background
In image forming apparatuses using electrophotography, such as copying apparatuses, facsimile apparatuses and printers, a latent image of image information is formed on a surface of a drum or belt-like shaped image bearing member by first uniformly charging the surface of the image bearing member and then exposing the charged surface with light modulated with the image information. The latent image is then developed by toner, and the developed toner image is transferred onto a recording medium, such as a sheet of paper directly or via an intermediate transfer member, thereby forming an image on the sheet of paper. The image forming apparatuses of this type include a developing device for developing the latent image by toner, and generally include a toner supplying device for supplying toner to the developing device as the developing device consumes the toner as a result of developing images.
A toner container containing toner is attached to the toner supplying device. Once the toner contained in the toner is consumed from being supplied to the developing device, the image forming apparatus generally stops the image forming operation and displays a message indicating that the toner container has run out of toner. The apparatus returns to an operable state once the toner container is replaced with a new toner container containing toner and the toner is supplied to the developing device.
As related art, Japanese Patent Laid Open Publication No. 2-277083 describes a toner supplying device having a plurality of toner containers, which are disposed near a developing device. The toner container chosen to supply toner to the developing device is changed by rotating the toner supplying device.
Japanese Patent Laid Open Publication No. 7-219329 describes a toner supplying device placed apart and connected to a developing device via a toner delivery device which delivers toner while mixing the toner with air.
Japanese Patent Laid Open Publications No. 4-80779 and No. 8-137227 describe a toner supplying device including a toner container accommodating device in which a plurality of toner containers can be attached. Toner discharged from each of the plurality of toner containers is merged with each other and conveyed to the developing device. Each of the plurality of toner containers is individually attachable to and detachable from the toner supplying device. The size of the toner container is made so that the container is easy to handle, and can be replaced with a new toner container without stopping the operation of the apparatus.
Japanese Patent Laid Open Publication No. 8-137227 further describes that the toner container accommodating device accommodates two toner containers. In addition, when a sensor detects non-existence of toner in a toner conveying pipe to a developing device, an agitator of one of the two toner containers, which has not been operated, begins to rotate to supply toner therefrom.
The Japanese Patent Laid Open Publication No. 4-80779 further describes a sensor to detect a toner container which is set in the toner supplying device, a detect device to detect non-existence of toner in the toner container, and a display device to display an indication to indicate that toner does not exist in the toner container of which the non-existence of toner is detected. In addition, the Japanese Patent Laid Open Publication No. 4-80779 describes that the toner container, which has first been set to the toner supplying device, is first set to start supplying toner to the developing device.
The Japanese Patent Laid Open Publication No. 8-137227 further describes that when a toner container is set to a toner container holder, a toner exit opening provided on an outer circumferential surface of the toner container is opened. Toner contained in the toner container is discharged from the toner exit opening by rotating an agitator provided inside the toner container. The agitator is rotated by an external drive device provided at a side of the toner container.
Also, Japanese Patent Laid Open Publication No. 7-5759 describes a toner container which includes an opening at one end to discharge toner. The opening is opened and closed by attaching and detaching a cap to the opening. The operation of attaching and detaching the cap is linked with an operation of an operator to replace the toner container, such that the operability of opening and closing the opening of the toner container with the cap is facilitated.
A toner supplying device including a plurality of toner containers, as described above in the background publications, has a problem in that the operability of attaching and detaching a toner container to and from the toner supplying device is poor. Further, rotating parts of the toner supplying device, which are exposed, may incur danger of hurting an operator when the operator attaches and detaches a toner container to and from the toner supplying device. Furthermore, toner scatters when a toner container is inserted into the toner supplying device through an insertion inlet for the toner container.
In addition, the toner supplying device including a plurality of toner containers, as described above in the background publications, has another problem in that, if an operator sets an empty toner container (i.e., a toner container containing no toner), the set empty toner container is not detected to be empty until an operating toner container becomes empty and the set empty toner container starts to be operated. This causes an intermittent supply of toner to a developing device, and thereby causes a decrease in the density of the toner in the developing device. Consequently, the resulting image quality is deteriorated. Stoppage of the image forming operation may also be caused.
Furthermore, the toner supplying device including a plurality of toner containers, as described in the above background publications, has yet another problem in that an operator cannot easily recognize both the non-existence of toner in each toner container and the nonexistence of a toner container itself in the toner supplying device. In addition, recognizing the remaining amount of toner in each of the toner containers is not easy. This causes a delay in replacing an empty toner container, which is erroneously set or a toner container whose toner is used up, and thereby causes a delay in supplying toner to the developing device. Consequently, toner is intermittently supplied to the developing device. Further, if an operator replaces a toner container whose toner is not completely used up without knowing that some toner remains in the toner container, toner may be scattered when the toner container is replaced. Thus, toner may be unnecessarily wasted.
In addition, toner supplying device in which a plurality of toner containers, as described above in the background publications, has still another problem because the operation of opening and closing a toner exit opening of a toner container with a cap is linked with the operation of replacing the toner container and moving the toner container to a position to start supplying toner therefrom. Therefore, if the toner container is replaced when the toner container is positioned at an interim position between the position where the toner container is replaced and the position where the toner container starts to supply toner therefrom, the cap is closed insufficiently, and thus the cap may fall inside a toner container accommodating unit, subsequently hindering the operation of replacing the toner container, or toner may scatter and stain the inside of the toner supplying device.
In addition, an image forming apparatus including a toner supplying device having a plurality of toner containers, as described above in the background art, has another problem in that attachment of the toner supplying device to the main body of the image forming apparatus at an assembling line, when the apparatus is installed at a user's place for use, or when the apparatus is overhauled is too complicated.